The Long Term Evolution (LTE) standard defines a interface, called the X2 interface, for communication between eNodeBs. The X2 interface supports user plane communications in the form of the X2-UP protocol, which is used to tunnel end-user packets between eNodeBs via GTP-U over IP or UDP as the transport layer protocol. The X2 interface also supports control plane communications via the X2-CP protocol, which is used to provide various functions over SCTP as the transport layer protocol. The X2-CP application layer protocol is X2AP.
The X2AP protocol provides the following functions, as described in 3GPP TS 36.423, hereby incorporated in its entirety: mobility management; load management; reporting of general error situations; resetting an X2 connection; setting up an X2 connection; eNodeB (eNodeB) configuration update; mobility parameter management; mobility robustness optimization; energy saving; X2 release; message transfer; registration; and removing an X2 connection. For example, X2AP can be used to facilitate user equipment (UE)-assisted network-controlled handovers and handovers without the involvement of a mobility management entity (MME).
However, as the number of eNodeBs increases, the number of point-to-point X2 connections between eNodeBs increases as the factorial of the number of nodes. This potentially results in a large volume of unwanted X2 signaling to perform basic coordination functions. A need exists for a system that can provide the benefits of X2 communications without these disadvantages.
The X2 interface generally defines a mechanism via which eNodeBs can directly interact with each other in order to perform functions like UE mobility management and load management effectively without involving the evolved packet core (EPC). The present disclosure describes how multiple internal eNodeBs managed within a virtual eNodeB may communicate with each other, and with eNodeBs outside of the virtual eNodeB, using the X2 interface.